The present embodiments relate to an apparatus for medical examinations.
Medical imaging methods based on x-rays have a wide diagnostic application range. In current and future applications, several recordings are performed from different positions. This aims at a three-dimensional reconstruction of images, such as are realized, for example, in computed tomography, and image sequences are used for the complete diagnostic imaging of body regions to be examined. Angiography is an important field in which these aims prevail.
Angiography applications are gaining increased importance in terms of intraoperative imaging. In addition to the classical tasks of angiography modalities, such as angioplasty in the case of static but flexibly positionable imaging recording system, modern methods of 3D image reconstruction are gaining in importance. To generate this data, image sequences are recorded across accurately defined trajectories of the image recording system. These techniques can be implemented, to a certain extent, with the existing modalities (e.g., DynaCT, SpiralCT). The reconstruction quality is, however, not far from that of a 3D reconstruction with the aid of a modern CT device. Angiography examinations are, in many cases, currently implemented with C-arms, which are provided in part with hinged carrier systems for the description of trajectories. A C-arm system that is suitably for angiography is described, for example, in DE 10 2007 021 717 A1.
To increase the reconstruction quality, attempts have been made to increase the rotational speed of the C-arm and retain very high repetition accuracies for previously calibrated motion sequences. Since, in current devices, the axle bearings are restricted by the running of cables to the C-arm or by structural restrictions, a very high starting acceleration and, at the end of the movement, a very high braking acceleration of the rotation are realized in order to adhere to these aims. This is done to achieve a high final speed. From the drive technology or structural design point of view, which forms the basis for maintaining the repetition accuracy, these maximum accelerations are severely restricted. A way out of this conflict of aims would be to implement a continuous rotation, during which the projection sequence is only recorded when the C-arm is accelerated and rotates about the isocenter at a constantly high speed. By decoupling the acceleration process and the x-ray image recording, considerably improved reconstruction results are likely to be achieved for the previously cited reasons on the basis of very uniform movements. The implementation of such a continuous rotation is nevertheless problematic. A slip ring on a central rotational axis for the C-arm rotation may transmit numerous forms of energy and information. The high voltage (e.g., 75 kV) cannot be transmitted with current slip ring systems but is instead converted from approximately 3 kV using a high voltage transformer carried on the rotating side of the slip ring.
Improved concepts for the slip ring integration have been proposed, with, depending on the kinematic structure of the movement system, differently effective conditions being provided for the integration. Classical devices from the high-end range (e.g., some products from the Siemens Artis series) are very well qualified to implement an improved slip ring concept. FIG. 1 shows one design provided.
If highly flexible movements by the emitter and detector are desirable, the slip ring integration reaches its limits. As a result of the condition of a central decoupling axis for each continuous rotation, the slip ring is fastened to the last axis of a serial kinematic chain (A6). An additional load provided by the slip ring and high voltage transformer at the end point of the kinematic chain is therefore borne by the robot. This cannot, however, be realized technically with the appropriate precision. FIG. 2 identifies the potential installed location.